Framework: Drop deprecations slated for 3.2 removal

[aduth]

This pull request seeks to remove deprecations slated for removal in the upcoming 3.2.0 release.

Specifically, this includes:

• wp.data.withRehydratation has been renamed to wp.data.withRehydration.
• The wp.editor.ImagePlaceholder component is removed. Please use wp.editor.MediaPlaceholder instead.
• wp.utils.deprecated function removed. Please use wp.deprecated instead.
• getInserterItems: the allowedBlockTypes argument was removed and the parentUID argument was added.
• getFrecentInserterItems selector removed. Please use getInserterItems instead.
• getSupportedBlocks selector removed. Please use canInsertBlockType instead.

See: https://wordpress.org/gutenberg/handbook/reference/deprecated/#3-2-0

Testing instructions:

Verify that there are no regressions in impacted behavior, and importantly that no references to deprecated behaviors exist in core code.

[tofumatt]

Looks like utils/deprecated.js is slated to be removed but the file and function are still there: https://github.com/WordPress/gutenberg/blob/remove/3-2-deprecations/utils/deprecated.js

Otherwise looks good.

[jorgefilipecosta]

I did some grepping and testing and things seem fine. I think the only thing missing is the removal of the deprecated wrapper from /utils/deprecated.

[mcsf]

We should mention this step of checking for deprecations in the release document.

[aduth]

Looks like utils/deprecated.js is slated to be removed but the file and function are still there: https://github.com/WordPress/gutenberg/blob/remove/3-2-deprecations/utils/deprecated.js

Nice catch. Our custom lint rule is dumb and can't find by the aliased originalDeprecated, hence my missing it. It's been updated in 1c5f0a7.

[aduth]

We should mention this step of checking for deprecations in the release document.

I might agree, but the document as written is more oriented to steps to undertake when already in the process of doing a release. Since the lint rule will forbid the merge of the version bump pull request anyways, I'm not sure it's of huge help. Maybe we should add a section on things to look out further ahead of the next release? (Maybe more as a step after a release)

[tofumatt]

Easily solved with a Release Checklist section, which totally belongs in the release docs. 🚲🏠

[aduth]

That would work, but only if it's the last step, not a pre-release step. Otherwise we risk reenforcing the idea that this be done at the time of a release, which I disagree with. 3.3 deprecations, for example, should ideally be removed immediately after the upcoming 3.2 release.

[tofumatt]

Oh, wait, right. Okay! I will add...

[aduth]

Sigh.. this wasn't meant to be included 😞 Only to help trigger the failing E2E locally.

[tofumatt]

Sorry I missed it too 😢